For instance, in a wiring of a wire harness installed in a motor vehicle, an electric wire is used which is obtained in such a way that a conductor such as copper or aluminum alloy is used as a core wire, a plurality of core wires are twisted together and the plurality of twisted core wires are coated with an electric wire coat. In such an electric wire, a terminal is attached to a terminal part of the conductor by crimping to connect the terminals to each other so that an electrical contact is established.
In a crimping part of the terminal and the electric wire (the core wires), reliability of connection may be occasionally deteriorated due to a decrease of contact pressure by creep or an aged deterioration. In order to solve the above-described problem, various techniques are proposed. For instance, a technique is proposed that, in an electric wire using aluminum for a core wire, the decrease of contact pressure due to creep or a mitigation of stress is prevented and a progress of the contact corrosion of dissimilar metals is suppressed to ensure a connection reliability (see, for example, patent literature 1). Further, another technique is proposed that a ring sleeve is used which has a serration formed to cause the surface of a conductor to be chamfered by crimping to prevent an aged deterioration of a crimping and connecting part as much as possible and improve reliability of electrical connection (see, for example, patent literature 2).